Chambered structure for wing sail

ABSTRACT

A so-called “wing” sail for a sailing vessel, having an airfoil section performing substantially in the manner of an ideal airfoil on either tack is described. A two-sided inner sail structure having resiliently deformable battens slidably engaging a track, fixed to the mast of the sailing device and extending rearwardly, the mast being rotatable about its vertical axis in either direction relative to vertical planes along the longitudinal axes of the sailing device and the boom. Translation of the two main surfaces of the wing sail as well as the surfaces at the clew corner while maintaining proper tension in the surfaces, is accomplished by opposed inflatable air bladders. An aerodynamic seal is provided along the trailing edge of the wing sail. A horizontal control bar is attached to the mast to control the pivotal movement of the mast. The outer sail members wrap, around the mast and are fastened to the mast by a zipper. Air bladders establish and maintain the desired airfoil shape, while allowing the batten members to flex when the wind moves from one side of the sail to the other.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally concerns a variable camber soft wing sail structure to improve the efficiency and performance of an aerodynamic lift structure for use on sailing devices.

[0003] The present invention particularly relates to a combined batten/bladder structure which can be used in a double sided wing sail to provide the sail with an airfoil shape.

[0004] 2. Description of the Previous Art

[0005] Historically, two main types of sail have been in use, either square or fore-and-aft in configuration. Square sails, used by sailing ships of olden days, sit in a position across the longitudinal axis of the hull of the boat, whereas, the latter are set along the axis of the hull.

[0006] Sailing in the early days was a difficult task. Ships were only able to sail before the wind, or with wind on the quarter. Encountering half wind or head wind meant that the ship had to stop and wait out the unfavorable wind direction. With gradual improvement of hull design, rigging and shape of sails, it became possible to sail a ship into the wind by a process called “tacking” or “beating up against the wind” wherein the ship follows a zig-zag path.

[0007] The functioning of a sail is complex. First, the sail acts as a straightforward wind-catching area. Because of the curvature imposed on it by the force of the wind, the sail develops an aerodynamic behavior much like an aircraft wing, creating a forward suction acting on the outside, convex side, of the bent sail. Moreover, in a sailing vessel with a foresail and mainsail, a jet propulsion effect materializes by the air streaming between the two sails, increasing the force behind the convex side of the mainsail. As a boat sails into the wind, the sail splits and bends the airstream towards the stern of the boat. The leading edge of the sail (the luff) separates the wind, causing the airflow to pass along both windward and leeward sides of the sail. The flow of air tends to go straight, but is forced by the sail to follow the sail's contour. The wind blowing across the windward side produces a pushing force referred to as drive. Concomitantly, wind blowing across the leeward (back side) tries to pull away from the surface of the sail, creating a lower pressure area at the back of the sail, thereby causing a pulling effect called lift. This lifting force accounts for up to 70% of the sailboat's power when sailing windward.

[0008] The foresail, or jib, increases the flow of air across the backside of the mainsail, helping to create an even lower pressure, producing more lift and increasing the pulling force. This venturi principle is typically referred to as the slot effect. All the above combined create a strong aerodynamic force exerted sideways. The keel, situated under the boat, and the hull as well, create lateral resistance, preventing sideways motion of the boat. The interaction of the two forces creates a resultant force moving the boat forward. The sails are trimmed so as to create maximum lifting force.

[0009] It is, therefore, desireable to create a shape for the wing sail that minimizes drag and increases lift. The most desireable configuration would be like that of an airplane wing, or airfoil. This has been the goal of sail designers for years.

[0010] 2.1 Prior Patents

[0011] U.S. Pat. No. 4,538,539 to Martin for a deformable shrouded water foil concerns an underwater appendage for sailboats, such as a keel or rudder, is fitted with an external shell-like shroud, which is placed around a core portion of the appendage such that the outer shroud forms a deformable water foil which is fastened on both sides of the core near its rear or trailing edge, and which shroud is everywhere else spaced away from the core.

[0012] This deformable shroud forms a hydrofoil, the leading edge of which can be displaced to either side of the core by means of inflatable bladders placed on either side of the core, thus creating a desired angle of attack for the deformable foil, either to port or starboard. Inflation of the bladder on the windward side of the boat creates an angle of attack to windward and also a bulging of the shrouded water foil on the windward side creating the desired hydrodynamic lift to counter the lateral component of the aerodynamic force on the sail. As the boat is turned through the wind, onto the opposite tack, the pressure on the bladder is relaxed as it becomes the leeward bladder, and pressure on the opposite bladder is increased as it becomes the windward bladder. Pressure on both bladders can be relaxed when no lift is desired as when running before the wind.

[0013] The deformability of the Martin keel will be seen to be of a like nature to the deformatibility of the sail of the present invention.

[0014] U.S. Pat. No. 4,064,821, Roberts, Jr., et al. Dec. 27, 1977, for a variable camber wing sail, describes a two-sided, spaced apart sail structure provided with resiliently deformable struts for each side, attached at one end to a beam, fixed to the mast of the sailing device, the mast being rotatable about its vertical axis in either direction relative to vertical planes along the longitudinal axes of the sailing device and the boom in a manner whereby a cam action is produced by the beam to deform or bend the struts in a manner so as to vary the camber of the wing sail, the amount of camber of one side of the wing sail being greater than the concave curvature of the opposed side thus producing an airfoil configuration. Provisions are made to permit translation of the two main surfaces of the wing sail as well as the surfaces at the clew corner while maintaining proper tension in the surfaces, and an aerodynamic seal is provided along the trailing edge of the wing sail. A horizontal control bar is attached to the mast to control the pivotal movement of the mast by a block and tackle attached between each end of the bar and the boom.

[0015] U.S. Pat. No. 4,624,203, issued to Ferguson, Nov. 25, 1986, for a batten structure for a wing sail, provides a batten structure which can be placed inside a double sided sail to provide a so-called “wing” sail having an airfoil section which can be close to an ideal airfoil on either tack. The structure includes a central beam, which engages the mast, a nose piece pivotably connected to the front end of the beam, and two flexible batten members each extending rearwardly from rigid connections on opposite sides of the nose piece and being slidably connected together at their rear ends. Spreaders which are movable relative to the beam connect the batten members and maintain its airfoil shape while allowing the batten members to flex when the wind moves from one side of the sail to the other.

[0016] 2.2. Terminology Defined

[0017] The following definitions are courtesy of Spinnaker Sailing of San Francisco.

[0018] Basic Sailboat Terms

[0019] Rudder: A spade-like object at the back of the boat that steers the boat by deflection of the water.

[0020] Gooseneck: The fitting that connects the boom to the mast. It works like a swivel allowing the boom to move up and down and swing from side to side.

[0021] Keel: The weighted fin at the bottom of the boat that keeps the boat from slipping sideways through the water.

[0022] Bow: Front end of the boat.

[0023] Stern: Back end of the boat.

[0024] Port: The left side of the boat when facing forward.

[0025] Starboard: The right side of the boat when facing forward.

[0026] Basic Standing Rigging

[0027] Mast: The large vertical spar that supports the sail and boom.

[0028] Boom: The horizontal spar used to hold and extend the foot of the main sail.

[0029] Basic Running Rigging

[0030] Halyards: Lines or wire rope used to hoist the sails.

[0031] Sheets: Lines used to control the sails. Trimming is tightening the sheet to move the sail towards the centerline of the boat and easing is letting it out.

[0032] Basic Sail Terms

[0033] Head: Top corner. (Where halyard connects to sail)

[0034] Tack: Bottom forward corner.

[0035] Clew: Bottom back corner.

[0036] Luff: Forward edge.

[0037] Foot: Bottom edge.

[0038] Leech: Backedge.

[0039] Terms That Usually Apply To Main Sails

[0040] Battens: Wood or plastic strips that act as stiffeners for the sail. They help keep the leech from fluttering.

[0041] Batten Pockets: Pockets sewn into the trailing edge of the sail to hold the battens.

[0042] Sailing Terms Underway

[0043] Close Hauled: Sailing as close to the wind as possible. (pointing)

[0044] Close Reach: Sailing between close hauled and beam reach.

[0045] Beam Reach: Sailing so that the wind is on the beam.

[0046] Broad Reach: Sailing so that the wind is behind the beam.

[0047] Running: Sailing so that the wind is directly astern. The jib and main sails will be on opposite sides.

[0048] Tacking: Turning the bow of the boat through the eye of the wind.

[0049] In Irons: The condition when the boat is pointed directly into the wind without steerageway.

[0050] Windward: The direction from which the wind is coming.

[0051] Starboard Tack: When the starboard side of the boat is windward.

[0052] Port Tack: When the port side of the boat is windward.

[0053] Leeward: The direction to which the wind is going.

[0054] Trim: To pull in . . . as in trim a sheet. (line)

[0055] Ease: To let out . . . as in ease a sheet. (line)

[0056] Beam: The widest section of a boat, generaily across the middle.

SUMMARY OF THE INVENTION

[0057] The present invention contemplates a main sail for use between a mast and a boom. The invention also contemplates a separate foresail at headstay for jib. The basic sail structure comprises a first and a second flexible exterior planar members, attachable substantially spaced parallel to each other between the mast and the boom, each in the substantial manner of a sail. The facing surfaces of the two planar members define a space between them. Within this space is a substantial supporting center inner sail whose luff is raised up a sail track. The sail structure also comprises a plurality of elongate, substantially rigid batten members, roughly spaced parallel to each other within the inner sail between the two planar members. Each batten member is mounted in batten pockets, at spaced-apart locations along the mast and is not attached to the mast, and each batten member extends reach roughly parallel to the boom

[0058] A first inflatable gas bladder is placed in a space between the plurality of batten members and a first flexible planar member. Similarly, a second inflatable gas bladder is found in a space between the plurality of batten members and a second flexible planar member. A pumping device is used for selectively inflating the first, or the second, gas bladder so that, pursuant to the selective inflation/deflation of both gas bladders, outward-facing surfaces of the two planar members assume the contours of the surfaces of an airfoil.

[0059] Accordingly, one of the principal objects of the present invention is to provide a substantially rigid inner sail member having resiliently deformable batten members attached at one end to a track fixed vertically along the mast of a sailing vessel, said inner sail extending horizontally to points of attachment to the leech of the main sail, the mast being rotatable about its vertical axis in either direction relative to the boom and the longitudinal axis of the sailing vessel.

[0060] Another principal object of the invention is to provide first and second outer sail members in a spaced-apart overlying relation to the inner sail member. The outer sail members wrap around the mast and are fastened by a zipper.

[0061] A further object of the instant invention is to provide a plurality of opposing inflatable air bladders separated by said inner sail. By selective inflating and deflating, said air bladders establish and maintain the desired airfoil shape, while allowing the batten members to flex when the wind moves from one side of the sail to the other.

[0062] A further object of the instant invention is to provide flap means connecting between respective pairs of the first and second sail members and the inner sail member to permit translation of the surfaces of the first and second sail members when the two-sided wing sail is adjusted by inflation/dflation, and/or rotation of the mast.

[0063] Yet another object of the present invention is to provide a laminated connecting relation between the trailing edges of the first and second outer sail members and inner sail member to permit said translation while effecting a seal between said trailing edges.

[0064] Certain complex compartmentalized inflatable sails, and mechanical camber systenms to create airfoil-type sails are known in the prior art; however, unlike the prior art, the batten/bladder sail construction of this invention is uncomplicated and relatively inexpensive to construct and to maintain.

[0065] These and other aspects and attributes of the present invention will become increasingly clear upon reference to the following drawings and accompanying specification.

BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Referring particularly to the drawings for the purpose of illustration only and not to limit the scope of the invention in any way, these illustrations follow:

[0067]FIG. 1 is a side elevation of a sailboat having a wing main sail of the type described herein, showing diagrammatically a basic shape and batten/bladder structure of a preferred embodiment of this invention.

[0068]FIG. 2 is a top plan view of a wing main sail of the type described herein, showing the wind dynamics propelling the boat substantially windward.

[0069]FIG. 3 shows the detail views of FIG. 2.

[0070]FIG. 4 is a top plan view of a main sail of the boat in FIG. 1, having a wing main sail of the type described herein, showing the wind dynamics propelling the boat substantially windward.

[0071]FIG. 5 is a side elevation of a sailboat having a wing main sail of the type described herein plus a foresail constructed in a similar manner, showing diagrammatically the basic shape and batten/bladder structure of a preferred embodiment of this invention.

[0072]FIG. 6 is a top plan view of a sailboat having a wing main sail of the type described herein and a foresail, showing the wind dynamics propelling the boat substantially windward, note the venturi effect of the wind rushing between the sails. As the wind enters between the fore and main sail, this venturi effect multiplies the force and effect of the wind, pushing and lifting with greater force upon the main sail.

[0073]FIG. 7 is a plan view of an alternate preferred embodiment to that of figure featuring a plurality of bladders.

[0074]FIG. 8 is a diagramatic view of the wing sail of this invention when sailing into the wind, showing a symmetrical configuration with both bladders slightly inflated.

[0075]FIG. 9 is a schematic diagram of a wing sail of this invention showing the configuration obtained when the mast is rotated windward to starboard, demonstrating the concave side obtained as a result of wind acting on the deflated starboard bladder side, and the convex bend due to the inflated leeward bladder on the port side.

[0076]FIG. 10 shows the reverse configuration obtained when tacking with the port side windward.

[0077]FIG. 11 is a schematic diagram of the gas distribution means of a preferred embodiment of this invention, showing the relationship of bladders, connecting conduits, equalizing valve and gas distribution transfer pump as one preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0078] Although specific embodiments of the invention will now be described with reference to the drawings, it should be understood that such embodiments are by way of example only and are merely illustrative of but a small number of the many possible specific embodiments to which the principles of the invention may be applied. Various changes and modifications obvious to one skilled in the art to which the invention pertains are deemed to be within the spirit, scope and contemplation of the invention as

[0079]FIG. 1 shows a small sailboat having a single wing sail 2. The hull of the boat, is not a part of the invention, and may be any one of a number of preferred conventional types. The shape of the sail is diagramatic only, and it is understood that sails may take various shapes under this invention. The mast 4 is of oblong form having its largest dimension fore and aft, and is designed to be rotatable at the mast step. Although the mast is described herein as oblong, it is well-known to practitioners in the art that the mast may also be round, square, or any other suitable shape. The mast carries a boom 10 and a series of batten structures within batten pockets in the inner sail as indicated at 19. The luff of the inner sail may have a bead [FIG. 3, Detail A, 56], which is slidable within the sail track 58 on the mast to allow and guide the sail to be raised in the conventional manner by pulling on a halyard. The point of attachment to the mast is described as a bead within a track, however, any other means of attachment as known to practitioners in the art may be used and remain within the scope of this invention.

[0080]FIGS. 2, 3, 4, and 7 are plan views of the preferred structure for the chambered wing sail of this invention. FIG. 2, and Details A, B, C, illustrate the interrelationship of the various components and attachments thereto.

[0081] Referring now to FIG. 2, a first 20 and a second 26 flexible planar members, preferably constructed from light-weight cloth, plastic or mylar material commonly used in sails, form an outer sail shell. These planar members are attached to each other, and are substantially spaced parallel to each other, between the mast 4 and the boom 10, as depicted in FIG. 1, in a substantially conventional manner of a sail. The facing surfaces of the two planar members define a space between them 57, containing a central inner sail 22, comprised of a plurality of elongate, substantially rigid, batten members, as shown in FIG. 1, 19. Each batten member 19, shown in FIG. 3, Detail C is slidably mounted inside a batten pocket 22 of the inner sail luff to reach [see Detail A]. The inner sail is slidably attached to the mast by an integral bead 56 running along the entire length of the luff of the inner sail fitted within a channel or track 58, or by spaced apart lugs along the mast. Attachment may be one of many other suitable means known to those versed in the art.

[0082] The space 57 [FIG. 2] in the outer sail shell 20 also contains a first [port] inflatable gas bladder 24 in a space defined by the plurality of batten members and said first flexible planar member 20. A second inflatable gas bladder 38 is contained in a similar space between the plurality of batten members and a second flexible planar member 26.

[0083] There is provided a system [FIG. 11] for selectively inflating the first 24, or the second 38 gas bladder. Subsequent to selective inflation of either gas bladder, the outward-facing surfaces of the two planar members of the outer sail shell 20, 26, assume the contours of the surfaces of an airfoil [see FIGS. 8-10]. The central part, or backbone, of the inflatable wing sail structure is the fully battened inner sail 22, slidably engaged [Detail C, 56] to a channel-like grooved sail track 58 vertically mounted on the mast 4, portions of which are connected to a forestay [Figure 1, 3], to further secure the sail without putting too much force on the mast.

[0084] The main sail body, therefore, is comprised of bilateral air bladders upwardly extending from the boom to near the termination of the masthead, and is disposed laterally to starboard 38 and port 24 sides of the central inner sail 22. The inner sail 22, the starboard 38, and port 24 air bladders, and the mast 4 are enveloped by the outer sail shell 20. The sail shell is bipartite, the starboard panel 20 conjoined with the port panel 26 at the leach, and the luff edges are removably united by a full-length zipper means [FIGS. 2, 4, 5, 30] located just portside of the mast when the air bladders are equally distended, immediately after it wraps around the dimensionally oblong rotatable mast 4. which acts as a leading pivot point of the sail.

[0085] The luff portion of the outer sail shell is laterally contained and secured by a plurality of loose outer shell retainer flaps FIGS. 2, 3, 28, each retainer flap attached at one end to the luff of the fully battened inner sail 22, and at the other end to the luff aspect of the outer sail panel 20, just reach to the mast 4. These flaps prevent lateral hyper-distention of said outer sail shell panels 20, 26 when both air bladders 24, 38, or any one of them, are fully inflated. Bladder retainer flaps, as shown in Detail B, 54, are welded to each of the air bladders 24, 38, and are attached to the fully battened, stiff inner sail 52. These flaps serve to prevent the bladders from excessive movement within the outer sail shell.

[0086]FIG. 3 depicts the configuration of the sail that is this invention when facing windward to the port side. The luff of the rotatable mast 4 is disposed into the wind source [large arrow]. The port side inner air bladder 24, is deflated causing the outer sail shell 20 to press against said deflated bladder and the stiff, fully battened inner sail 22. The inner sail is opposingly supported by the fully inflated starboard air bladder 38, which also presses against the outer sail shell panel 26, forcing it to conform to the inflated air bladder's 38 convex shape. The spatial configuration and the proportions of the inner and outer components of the sail impart a smooth convex structural aspect to the rearward face of the sail, closely approximating the desired airfoil configuration for attaining maximum power, speed and efficiency.

[0087] In FIG. 5 is a small sailboat with two sails, a main sail and a foresail 62, containing an inner bladder system as described hereinabove. This configuration is especially advantageous because it allows one to take advantage of wind dynamics, creating a “venturi effect” seen in FIG. 6. As the wind flows between the sails at A, it picks up velocity and force at B, causing greatly increased push and lift at C against the wing sail.

[0088] Another preferable embodiment is depicted in FIG. 7, wherein the two bladders flanking the inner sail are replaced with a plurality of bladders. This configuration would find practicality in larger sails. The bladers would be filled using a manifold, or they could coupled by interconnected airways. The bladders would be appropriately sized to give the sail the desired contour.

[0089]FIGS. 8, 9, and 10, show the chambered structure of the wing sail of this invention under the various tacking conditions normally encountered.

[0090]FIG. 8 shows the usual configuration of the sail and its inner components when heading windward. Both bladders 24, 38, are distended and the sail takes on a smooth uniform shape suited for cutting directly into the wind. Note the position of the zipper 30, and the luff retaining flaps 28, holding together the outer sail shell 20, 26. The oblong rotatable mast 4, is directed forward into the wind, and the inner sail 22, and flanking air bladders 24, 38, form a symmetrical, smooth sail surface for maximum forward speed under these wind conditions.

[0091]FIG. 9 depicts the sail when facing starboard wind conditions. The previously symmetrical sail now takes on the asymmetric shape of an airplane wing, with its portside bladder maximally distended. The starboard bladder is completely deflated, allowing the wind to press against the outer sail shell, thereby slightly flexing the fully battened inner sail in a concave configuration. The distended port bladder forms a smooth convex surface, allowing the sail to act like an airfoil, resulting in maximum lift, and power from the opposing wind. Note the position of the zipper 30.

[0092]FIG. 10 demonstrates the mirror-opposite effect when sailing windward portside. Again, note the position of the zipper 30.

[0093]FIG. 11 shows the manner in which gas volume within the bladders 24, 38, is regulated by a three-way transfer equalizing valve 66, and air distribution transfer pump 64, via bifurcating transfer tubing into and out of the portside and starboard air bladders 24, 38, respectively. There is also shown a valve-controlled exhaust port for purging air from the stystem. As seen in FIG. 1, there is a tubing extending into the bladders at the bottom 14, and top 18, aspects of the sail.

[0094] In accordance with these and other possible variations and adaptations of the present invention, the scope of the invention should be determined in accordance with the following claims, only, and not solely in accordance with that embodiment within which the invention has been taught. 

What is claimed is:
 1. A sail for use between a rotatable mast and a conventional boom, comprising: a first and a second flexible planar members, attachable substantially spaced parallel to each other between the mast and the boom each in the substantial manner of a sail, facing surfaces of the two planar members defining between them a space; a plurality of elongate substantially rigid batten members located roughly spaced parallel to each other in the space between the two planar members, each batten member slidably mounted at a one end to the mast at spaced apart locations along the mast and each batten member extending roughly parallel to the boom to the reach of the planar members; a first inflatable gas bladder in a space between the plurality of batten members and a first flexible planar member; a second inflatable gas bladder in a space between the plurality of batten members and a first flexible planar member; and means for selectively inflating the first, or the second, gas bladder so that, consequent the selective inflation of both gas bladders, outward-facing surfaces of the two planar members assume the contours of the surfaces of an airfoil.
 2. The sail according to claim 1 wherein each batten member is slidably engaged to a sail track vertically mounted on the mast.
 3. The sail according to claim 1 comprising a fully battened inner sail.
 4. The sail according to claim 1 wherein each bladder is secured by bladder retainer flaps welded to the bladder and attached to the inner sail.
 5. The sail according to claim 1 wherein the first and second flexible planar members form an outer sail shell.
 6. The sail according to claim 1 wherein the outer sail shell luff edges wrap around the mast, which mast acts as a pivot point of the sail.
 7. The sail according to claim 1, wherein said luff edges are removably united by a zipper means.
 8. The sail according to claim 1 comprising a plurality of loose outer shell retainer straps, each retainer strap attached at one end to the luff of the fully battened inner sail and at the other end to the luff aspect of the outer sail just reach to the mast.
 9. The sail according to claim 1 wherein inner and outer sail shells are secured to each other at the reach of said sail.
 10. The sail according to claim 1 wherein gas within the bladders is regulated by a three-way transfer equalizing valve.
 11. The sail according to claim 1 comprising means to purge gas from the conjoined bladders.
 12. The sail according to claim 1 further comprising a gas distribution transfer pump.
 13. The sail according to claim 1 wherein the front of the mast facing windward and the inflated leeward bladder opposed by the deflated windward bladder together operate to form a wing-like airfoil, smoothly concave windward and smoothly convex leeward, thereby providing substantial lift and minimal drag. 